When an accident of aspiration or swallowing occurs during dental treatment, the patient would fall into severe clinical condition such as pneumonia, peritonitis, sepsis, and even death, unless a dentist immediately judges the patient's situation. As most dental material is radiopaque, radiography of a chest or an abdomen allows to see the accidental materials. From 1995 to 2002, 35 radiographic examinations were performed after the accidents at Tokushima University Dental Hospirtal. Mean of accidents was 4.4 cases a year. The incidence was 0.004% in the cumulative numbers of dental examinations. The location of accidental material on the radiography was clearly observed in 18 among 35 cases. Radiography of multiple times was performed 13 in 18 cases in order to confirm the excretion. In 5 cases, accidental materials were not confirmed to excrete. Furthermore, there were many cases in which clinical records about accidents were not described. Present findings indicate that it is necessary to detect precisely the location of accidental materials and that radiographic detection is very important.